Generally speaking the trend is to get rid of so-called useless gestures but they continue over modes of communication, generations and societies. If they were useless they would have disappeared long ago.

Manners can be a matter of life and death in some cases. I remember a situation where an uncle killed his nephew because the nephew addressed him in the wrong manner. It's not unique. We regularly hear of people fighting because they felt disrespected. Respect and disrespect are fundamental to humans.

Manners are important.

> Countries with a lot of politeness (e.g. Japan) don't seem to be any better at communicating and cooperating than countries with very little (e.g. Finland). If anything I would guess there's a negative correlation.

Context matters. Population density of Japan makes it a different game.